With the popularization of mobile terminals, such as smartphones, the average amount of data consumed by mobile communication users has increased significantly, and thus there is an ever-increasing demand for higher data rates. In general, a method for providing a high data rate may be divided into using a wide frequency band and increasing frequency utilization efficiency. However, it is very difficult to provide a higher average data rate through the latter method. This is because the frequency utilization efficiency supported by contemporary communication technologies has already nearly reached the theoretical limit, which makes it very difficult to achieve a further increase in the frequency utilization efficiency through technical improvements. Accordingly, under the present circumstances, a more feasible method for increasing data rates is to provide a data service over a wider frequency band. With regard to this, an available frequency band must be taken into consideration. Under the current frequency distribution policy, available broadband communication bands of 1 GHz or greater are limited, and the actually selectable frequency bands include only the millimeter wave bands above 30 GHz. In such high frequency bands, unlike the 2 GHz band used by the conventional cellular systems, signals suffer severe distance-dependent attenuation. Due to the signal attenuation, when a base station uses the same power as in the conventional cellular systems, its service coverage may be considerably decreased. In order to solve this problem with the service coverage, a beamforming technique is widely used to increase the transmission/reception efficiency of an antenna by concentrating transmission/reception power in a narrow space.